Velocity is a relationship of displacement over time. Speed and velocity differ. Speed is the change of distance with respect to time where as velocity is the change of displacement with respect to time.  For what we are looking at here speed and velocity can be interchangable, because our distance and displacement is one in the same.  So when looking at these animals speeds we really need to look at their distance vs time.  We can think of it as the change is distance over the change in time.  Using the following equation we can calculate this where delta s is change is distance and delta t is change in time; v =  Δs/ Δt